Many electrically powered tools operate via ordinary household AC current, and therefore must be plugged into an electrical wall outlet during operation. AC wall current has been used for many years to operate tools such as radial saws, drills, routers, sanders, and the like. Additionally, in recent years AC current has begun to be used widely on outdoor lawn tools that formerly were gasoline powered, such as lawnmowers, tree trimmers, chainsaws, weed eaters, and the like. Electrically powered tools are typically provided with a built-in electrical cord that extends from the body or handle of the tool. The built-in cord may vary in length from anywhere from two inches (a "pigtail" cord) to upwards of twenty feet and more. The built-in cord ends in a standard male plug that can be plugged into either a wall outlet or an extension cord. When an extension cord is used, the male plug of the built-in cord is plugged into the female socket of the extension cord, while the male plug of the extension cord is plugged into a wall outlet.
The present invention is directed to the problem of separation of power cords without relying on friction between the metal conductors of the plugs to maintain the connection. The contact pressure (friction) of the metal parts of conventional plugs is designed for nothing more than adequate pressure to maintain electrical integrity between the two cords. Separation occurs frequently when a built-in cord of an electrical tool is plugged into an extension cord, and also when two electrical cords are plugged together. The problem of cord separation occurs with ordinary workshop power tools, but is particularly widespread with the use of power lawn tools, which are typically carried about the yard during operation. Because lawn tools are typically used large distances from the wall outlet, a portion of the extension cord can easily become snagged around or under a tree, fence, lawn furniture or the like. When this occurs and sufficient tension develops in the plug connection, such as where the operator of the tool does not notice that the cord has become snagged or the operator has reached the limit of the length of the cord, the end of the built in cord separates from the female end of the extension cord. This can result in dangerous situations. For example, the cords may momentarily separate, breaking the electrical connection and causing the tool to shut off, but then, upon release of tension on the cords, reestablish electrical connection, causing the tool to start up again.
A number of devices have been constructed for holding and securing electrical cords together. Most users of electrical tools are familiar with the method of tying or intertwining the ends of two electrical cords together and then plugging the ends of the cords together. When tied together in this manner, strain or tension that develops in the cords is borne by the knot holding the cords together, such that the cords cannot separate. One disadvantage of this method is that it can cause damage to the outer insulation of the cords, most likely at the end attachments of the cords, i.e. the cords, particularly over the course of time. Additionally, it is sometimes difficult to separate the knot.
As shown in FIG. 1, the prior art includes a restraining device built into the handle 100 of an electrically powered tool. This embodiment includes an eyelet member 102 and a hook member 104 that extend downward from the handle 100 of the tool. As shown in FIG. 1, a folded portion of an extension cord is passed through the eyelet 102 and then looped over the hook 104. A female end 95 of an extension cord 90 is then plugged into a male plug 82 of the tool 100. A fundamental disadvantage of the prior art embodiment of FIG. 1 is that if the hook member 104 or the eyelet member 102 breaks, the device can no longer be used to hold a cord onto the device. The built-in holding device becomes useless for its intended purpose, and cannot be replaced. The disadvantage of this design is further heightened by the fact that remnant pieces of the broken components cannot be readily removed from the handle of the tool, and thus become potential hazards. The broken remnants may catch on clothing or other items, which can be particularly dangerous with powerful electric tools such as chainsaws and tree trimmers. Additionally, because the built-in restraining device cannot be transferred to other electrical cords, it serves only to hold a cord onto the particular power tool that has the built-in restraining device.
A number of devices have been devised for restraining electrical cords. Most such devices provide an elongated or bar-like member having at least two symmetric cord holders spaced apart along the elongated member. See U.S. Pat. No. 3,781,761 (Harwood), U.S. Pat. No. 4,504,106 (Fechter), U.S. Pat. No. 5,255,866 (Campolo), U.S. Pat. No. 5,514,004 (Swanson), and U.S. Pat. No. 5,549,482 (Langlais et al). One disadvantage of such devices is that they require each cord to be pulled tight around a respective cord holder, which can cause damage to the outer insulation of both cords. Because each cord must be bent around its respective cord holder, an unnecessary amount of crimping and bending of cords is required. Additionally, it becomes difficult to unplug the cords when on the device. Another disadvantage of such devices is that they are not configured to remain in place on one of the cords once the electrical cords are separated. Once separated from the cord, the device can easily become misplaced. Additionally, because such devices have symmetrical holders on either end of an elongated member, they tend to be bulky. Finally, an important disadvantage of such designs is that they cannot be used with short cords, such as the pig-tail cords found on many power tools.
U.S. Pat. No. 5,582,524 (Sanner et al) discloses a cord-to-cord restraining device comprising an elongated base having a first end and a second end, a first eyelet secured to the base member closer to the first end, and a second eyelet secured closer to the second end. The eyelets are sized for receiving loops of electrical cords. First and second hook members are secured to the base between the two eyelets. A looped portion of a first electrical cord is passed through one eyelet and looped over a corresponding hook member, while a looped portion of a second electrical cord is passed through the other eyelet and looped over the other hook member. The Sanner design suffers from the above mentioned disadvantages.
Other configurations have been used as cord-to-cord restraining devices. U.S. Pat. No. 4,610,494 (Schauber) discloses a flexible loop through which the two cords can be passed. The Schauber device requires a fairly large loop, because the plugs of each cord must pass through the loop. German Patent DE 3343233 (Bosch) discloses a retaining lug formed or built into the end of a plug connector and having two profiled hooks for engaging an electrical cord.
There is thus a need for a cord-to-cord restraining device that overcomes the foregoing problems and shortcomings of the prior art.